The following techniques have been disclosed as techniques of efficiently controlling a motor by using an efficiency map in a configuration of driving drive wheels (wheels) with the motor disposed on an electric vehicle (EV) that is a mobile body.
In a first technique, an efficiency map is selected according to the state of charge (SOC) of a battery and a gear stage is selected based on the selected efficiency map such that efficiency is optimized. Even if output characteristics of a motor vary in association with a change in the SOC and the actual efficiency map changes, the gear stage can be selected according to the resulting efficiency map or an efficiency map close to this map and total efficiency of a drive device of an electric vehicle can always be optimized (see Patent Document 1).
In a second technique, motor efficiency during power running of a motor is set based on motor rotation speed Nmot and motor torque Tmot as an efficiency map in advance from experiment, and single motor efficiency Emot is obtained from the efficiency map depending on the motor rotation speed Nmot and the motor torque Tmot. Motor efficiency during regenerative control of the running motor is also set in advance from experiment in the same way and the single motor efficiency Emot is obtained from this efficiency map during regenerative control (see Patent Document 2).
In a third technique, multiple rotary electric machine efficiency η maps related to an effective magnetic flux are included, and efficiency values (output power/input power of a rotary electric machine) at a required rotation count and required torque are acquired from the multiple rotary electric machine efficiency η maps to select an effective magnetic flux indicating a value of the highest efficiency among the multiple efficiency values acquired from the multiple rotary electric machine efficiency η maps (see Patent Document 3).    Patent Document 1: Japanese Laid-Open Patent Publication No. H5-168109    Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-231102    Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-213429